1. Field of the Invention
The present invention relates to an ester group-containing siloxane compound which can be blended with a coating composition, a binder, cosmetics or the like in order to improve its water repellency, lubricating properties and the like, and it also relates to a preparation method of the siloxane compound.
2. Description of the Related Art
Some methods for synthesizing ester group-containing silanes by a hydrosilylation of an acrylic acid ester or a methacrylic acid ester and a silane have heretofore been reported. For example,
(a) Y. KISO; J. Organometal. Chem., Vol. 50, p. 297-310 (1973), PA1 (b) I. OJIMA; J. Organometal. Chem., Vol. 111, p. 43-60 (1976), and PA1 (c) E. YOSHII; Chem. Pharm. Bull., Vol. 22 (11), p. 2767-2769 (1974). PA1 a. a siloxane compound of the present invention in which p=2 and n=0, PA1 b. a siloxane compound of the present invention in which p=2, l=0, n=0 and R.sup.2 =a methyl group, PA1 c. a siloxane compound of the present invention in which p=2, l=0, n=0, R.sup.2 =a methyl group, R.sup.3 =a butyl group and s=0, PA1 d. a siloxane compound of the present invention in which p=2, l=0, m=0, n=0, R.sup.2 =a methyl group and R.sup.3 =a methyl group, PA1 e. a siloxane compound of the present invention in which p=2, l=0, m=0, n=0, s=0, R.sup.2 =a methyl group and R.sup.3 =a methyl group, and PA1 f. a siloxane compound of the present invention in which p=2, l=0, n=0, R.sup.2 =a methyl group, R.sup.3 =A and s=0.
However, there has been no example in which the above hydrosilylation is carried out by the use of a siloxane compound in place of a silane under usual reaction conditions. In the case that the hydrosilylation is done by the use of the silane compound, several problems have been present. For example, a very specific catalyst needs to be used, and it is impossible to selectively produce a .beta.-silyl compound. Accordingly, an ester group-containing siloxane compound cannot be prepared by the hydrosilylation using the silane compound under the usual conditions.
Furthermore, Japanese Patent Application Laid-open No. 291980/1995 discloses a method for preparing an ester group-containing silane by the hydrosilylation of methyl acrylate and the silane. However, any technique of using the siloxane compound has not been disclosed. According to this disclosed technique, an .alpha.-silyl compound in which a silicon-carbon bond can easily react with an alcohol can be selectively produced, but a chemically stably .beta.-silyl compound cannot be selectively produced.
Because of the above situations, in a conventional case where the ester group-containing siloxane is prepared, a polysiloxane having a hydroxyl group or a carboxyl group at the terminal is used as a starting material, and an acid or an alcohol is reacted with this polysiloxane to obtain the ester.
However, the conventional preparation method proceeds via a terminal hydroxyl group-containing polysiloxane or a terminal carboxyl group-containing polysiloxane as described hereinbefore, and hence a preparation process is prolonged, which inconveniently leads to the increase of cost. Additionally, in the above esterification reaction, an acid catalyst is usually used, and owing to this acid catalyst, there is a problem that an undesirable side reaction such as the cleavage of a siloxane bond occurs.